Modifier for concrete and cement formulations and methods of preparing the same

ABSTRACT

Disclosed are wax emulsion modifiers for concrete and cement formulations and methods for preparing the same. The modifiers are applicable to roller compacted concrete (RCC), used for manufacturing of industrial floor slabs, dams and roads. This invention also relates to conventional Portland cement concrete mix designs or other applied concrete mixes for formed structural shapes and transport road mix designs, providing a more rapid dehydration of the aqueous phase, without sacrificing strength, yet providing a higher density that remains workable at the point of application. The modifier of the invention may be utilized for either the initial soil/cement base or for the final/finished placement.

RELATED APPLICATION DATA

This application is a continuation application of co-pending U.S. patentapplication Ser. No. 12/406,579 filed Mar. 18, 2009, which applicationclaims benefit to U.S. Provisional Application Ser. No. 61/037,761 filedMar. 19, 2008, the entire contents of both applications are incorporatedby reference herein.

FIELD OF THE INVENTION

The present invention relates to wax emulsion modifiers for concrete andcement formulations and to methods for preparing the same. The modifiersare applicable to roller compacted concrete (RCC), used formanufacturing of industrial floor slabs, dams and roads. This inventionalso relates to conventional Portland cement concrete mix designs orother applied concrete mixes for formed structural shapes and transportroad mix designs, providing a more rapid dehydration of the aqueousphase, without sacrificing strength, yet providing a higher density thatremains workable at the point of application. The modifier of theinvention may be utilized for either the initial soil/cement base or forthe final/finished placement.

BACKGROUND OF THE INVENTION

Roller Compacted Concrete (RCC) is concrete, but it is placed bynon-traditional methods which require a drier or stiffer consistency.RCC can have a much broader range of material properties thanconventionally placed concrete, for example, it can use aggregates notmeeting normal requirements, it can be placed at very high productionrates, and it can be much less expensive.

By definition, RCC is concrete comprising a mixture of cement, sand,aggregate, such as gravel, stone, sand and the like, and water, having aconsistency allowing it to be compacted with a heavy vibratory roller,for example, a ten-ton roller intended for asphalt and granular base.RCC is usually mixed in a continuous process, rather than in batches,delivered with trucks or conveyors, spread in layers using a bulldozer,and given final compaction with a vibratory roller.

RCC has generally been used for applications such as dam construction,pavement and bridge deck construction requiring a thick topping, usuallytwo inches, as an essential element to achieve the required strength andfatigue life of the exterior slabs.

Conventional poured mass concrete is designed to have the highestfluidity by use of water and additives, the RCC formulation has the sameingredients as conventional concrete, i.e., cement, water, andaggregates, but unlike conventional concrete it is a drier mix stiffenough to be compacted by vibratory rollers. The pressure applied duringthe compaction phase of the mix implies a need of the highest possibleinitial density to ensure superior compressive strength, this can bereached by reducing the water level, however if the level is below thehydration level, the cured concrete will not reach the optimumproperties. Therefore, current RCC mixes still have a water content thatis at best a compromise between the full cure and the lowest slump ofthe concrete during the application of the vibratory rollers. There is aneed in the industry for an RCC formulation that has the right amount ofwater to achieve a correct amount of hydration and also has the highestinitial compressive strength.

Surfactants decrease the need for excess water, while making theconcrete mix pourable, as if excess water was present. When surfactantsare introduced into the concrete, the result is a less porous andsomewhat stronger product. The strength increase is attributed to lowerwater/cement ratio and decrease in porosity. While surfactants improvethe resistance to water penetration, surfactants alone provide toolittle improvement to be considered a solution to the problem.

Attempts have been made to increase the early strength of cementaggregate products, particularly concrete blocks, concrete masonryunits, and the like, by adding an accelerator, such as calcium chloridetriethanolamine or sodium silicate, to the mix or subjecting the productto steam or using type III cement. However, the addition of theseaccelerators, or the use of steam, increases the cost of producing theproduct and often its production time.

Another attempt provides for compositions, and a process for improvingthe early strength of cement aggregate products, in a stabilized aqueousemulsion with a surfactant such as alkali metal salts of fatty acids,alkali metal salts of sulfated fatty acids, alkali metal alkyl sulfates,alkali metal alkyl sulfonates, alkali metal aryl sulfonates, alkalimetal alkyl lauryl sulfonate, alkali metal salts of alkylatednaphthalene, alkali metal salts of lignosulfonic acid, condensationproducts of ethylene oxide and polyalkylene glycols, fatty acidglycerides, fatty acid amides, polyethylene sorbitol esters of fattyacids, quarternary ammonium halides, sorbitan esters, sulfonated orsulfated fatty acid esters or amides, and sulfonic acid. Results wereachieved with sodium lignosulfonate as the surfactant, particularly withslack wax as the waxy substance in the emulsion.

The prior art indicates that the introduction of a wax in a solvent intothe composition of water, cement, and aggregate used to produce aconcrete product caused the resulting concrete to have substantiallyless strength than the concrete product produced from a substantiallyidentical composition without the wax. It is believed that the waxcoated the aggregate particles and inhibited the adherence of the cementpaste to the aggregate causing the weakening as measured by testing thecompressive strength. Therefore, the use of waxes in cement formulationsfor RCC application was not previously advisable.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides an aqueous emulsion,useful for providing a cementitious composition with an initialcompressive strength of at least 2400 psi, which includes a paraffinhydrocarbon wax, a saponifiable wax, a saponifier, and an optionaldispersant.

In another embodiment, the present invention provides an aqueousemulsion, useful for providing a cementitious composition with aninitial compressive strength of at least 2400 psi, which includesessentially only a paraffin hydrocarbon wax, a saponifiable wax, asaponifier, a dispersant and water.

In another embodiment, the present invention provides a method forpreparing an aqueous emulsion, that provides cementitious compositionswith an initial compressive strength of at least 2400 psi, whichincludes the steps of combining water, a paraffin hydrocarbon wax, asaponifiable wax and a saponifier, heating the combination to atemperature of between about 185° F. (85° C.) to about 205° F. (96.1°C.), then homogenizing the mixture.

In another embodiment, the present invention provides for a cementitiouscomposition, including dry cement, admixed with about 1 to about 25gallons per cubic yard of an aqueous emulsion which includes a paraffinhydrocarbon wax, a saponifiable wax, a saponifier, and an optionaldispersant.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that the aqueous emulsion modifiers of the invention,which include a paraffin wax, a saponifiable wax, a saponifier, andoptionally a dispersing agent, when admixed into concrete design mixes,provides for improved properties and advantages.

In one embodiment the paraffin hydrocarbon wax has a melting point inthe range of about 50° C. to about 70° C. In another embodiment theparaffin wax contains one or more C_(n)H_(2n+2) hydrocarbons, where n isan integer between 18 and 42. The paraffin wax may comprise about 20 toabout 60 wt % of the emulsion. In another embodiment, the paraffin waxmay comprise about 30 to about 50 wt % of the emulsion.

In one embodiment, the second wax is a Montan wax, also known as lignitewax, having a melting point in the range of 70° C. to 100° C. and anacid value greater than 25, and a saponification number greater than 85.The second wax may also be from a class of waxes characterized in thatit has both an acid value and a saponification value, for example,carnauba wax, candelilla wax, bayberry-myrtle wax, Japan wax, and thelike. The second wax may also be a combination or any subset of suchsaponifiable waxes. In one embodiment, the second wax is present in theemulsion is between about 0.01 to about 20 parts, by weight, per 100parts of the paraffin wax. In another embodiment, the second wax ispresent in an amount of between about 0.01 to about 10 parts, by weight,per 100 parts of the paraffin wax. In another embodiment, the second waxis present in an amount of between about 0.5 to about 7 parts, byweight, per 100 parts of the paraffin wax. In another embodiment, thesecond wax is present in an amount of between about 0.02 to about 5parts, by weight, per 100 parts of the paraffin wax.

Saponification of such waxes, as is known in the art, may beaccomplished by combining the wax with a strongly basic material such asan ammonia hydroxide or an alkali metal hydroxide such as potassiumhydroxide, sodium hydroxide or lithium hydroxide. The amount ofsaponifier needed may be calculated based on the saponification value ofthe wax. For one example, the saponification value divided by 1000equals the grams of potassium hydroxide to add per gram of wax. ForMontan wax, at least 0.1 part potassium hydroxide, by weight, or lessthan 1 part by weight sodium hydroxide, or more than 0.1 part by weightammonium hydroxide is required per part of Montan wax. The actual amountof the alkali metal or ammonium hydroxide required can be readilydetermined by those skilled in the art.

In certain embodiments of the present invention a dispersing aid, orfluidity modifier, may be useful. Such dispersing agents are stronglipophiles, which are, consequently, good defoamers. One such dispersingagent is poly(oxy-1,2-ethanedyl), alpha-phenyl-omega-hydroxy styrenate.A salt of polynaphthalenesulfonic acid may also be utilized as adispersant/surfactant. The salt may be produced by the reaction ofpolynaphthalenesulfonic acid and a saponifier. One commerciallyavailable polynaphthalenesulfonic acid is DISAL GPS, which may beobtained from Handy Chemical, Montreal, Quebec, Canada. DURASARPolynaphthalene sulfonate calcium salts, also available from HandyChemical, Montreal, Quebec, Canada, may also be used as dispersingagent. In one embodiment, the dispersant/surfactant may comprise about0.1 to about 5 wt % of the emulsion. In another embodiment thedispersant/surfactant may comprise about 0.25 to about 5 wt % of theemulsion.

In one embodiment, the ratio between the dry blend cement and theemulsion of the invention is between about 1 to about 25 gallons percubic yard of mix (about 3.8 to about 94.6 liters per cubic meters ofmix). In another embodiment, the ratio between the dry blend cement andthe emulsion of the invention is between about 1 to about 7 gallons percubic yard of mix (about 3.8 to about 26.6 liters per cubic meters ofmix). When blended with cement, aggregates and sand, the emulsion of theinvention provides an initial compressive strength of at least 2400 psiwhich increases further with curing to the design strength, which istypically at least about 5000 psi.

In one embodiment, the wax emulsion modifier of the invention is admixedwith a cementitious composition, typically Portland cement and class 1fly ash. In another embodiment, the wax emulsion modifier of theinvention is not applied to the surface of a cementitious composition.

In one embodiment, in cement based systems, the wax emulsion modifier ofthe invention, when admixed in to concrete designs, is believed toprovide lubricity allowing for greater compaction which results inhigher density with equivalent compactive forces. The reduction in thewater/cement ratio in cement designs results in greater strength of atleast >40% at 7 days, reducing the optimum moisture content by atleast >35% significantly increasing the density by decreasing air voidsnormally experienced with these mix systems. Benefits for such systemsincorporating the wax to emulsion modifier include higher compactivedensity or the same density with less compactive effort, lower waterdemands for compaction, lower cement requirements to obtain equivalentstrength (>2%), and improved workability. Further advantages includedlower transportation cost resulting from transporting less water anddecreased permeability due to the reduction of interconnected air voids,which improved water resistance. Benefits additionally includeaesthetical advantages such as in the surface appearance of RCCincorporating the wax emulsion modifiers of the invention.

In another embodiment, in final placement RCC mix designs the admixingof the wax emulsion modifier of the invention results in at least a >20%strength gain in 7 days and at least >10% in 28 days. Incorporating thewax emulsion modifer of the invention into such mixes allows for lowercement content to gain equivalent strengths allowing lower placementthicknesses to carry the same design loads.

EXAMPLES

Table 1 lists the formulation of the modifier utilized in the examples.In a typical preparation, the water and water soluble components werecombined then heated to a temperature of between about 185° F. (85° C.)to about 205° F. (96.1° C.). The wax compounds were incorporated andalso heated to a temperature of between about 185° F. (85° C.) to about205° F. (96.1° C.). The aqueous and wax mixtures were then combined andthe resultant mixture was then placed in a homogenizer. Withhomogenization it is preferred that a distribution of micelle diametersranging from about 0.6 micron to about 1.8 micron be achieved. However,the distribution of micelle diameters may range from about 0.5 micron toabout 2.5 micron. This level of homogenization may be attained, forexample, by using a dual orifice homogenizer operating at from about2,000 to about 4,000 psig.

TABLE 1 Modifier Formulation Component Weight Percent (wt %) ParaffinWax 38.68 Montan Wax 1.00 DISAL¹ Dispersant 1.00 45% aq. KOH 0.25 Water59.07 ¹DISAL is a polynaphthalenesulfonic acid dispersant available fromHandy Chemical, Montreal, Quebec, Canada.

Table 2 sets forth a typical RCC mix design incorporating the waxemulsion modifier of the invention.

TABLE 2 RCC Mix Design for 1 Cubic Yard Material Pounds (kg) Type 1Cement 300 (136)  Class C Fly Ash 125 (56.7) Concrete Sand 1263 (572.9)Size 57 Uncrushed Gravel 2195 (995.6) Water 109 (49.4) Wax EmulsionModifier of the Invention 21.25 (9.64) 

Table 3 illustrates that the wax emulsion modifier of the inventionprovides higher density with equivalent compactive forces. The reductionin the water/cement ratio in soil/cement designs results in greaterstrength, >40% at 7 days, reducing the optimum moisture content by >35%significantly increasing the density by decreasing air voids normallyexperienced with these mix systems. (ALDOT 416-05 Soil-Cement).

When the emulsion of the invention is used, the quantity of watercontained in the emulsion is deducted from the initial water quantityfrom the composition without emulsion. Mixing was continued until themixture was uniform in consistency and hydration had occurred noted by avisual change in the consistency of the mix.

TABLE 3 ALDOT 416-05 Soil-Cement Replacement ASTM D 558 METHOD A WITHCONTROL ADDITIVE MAXIMUM/CORRECTED DRY DENSITY (pcf) 121.1 126.4OPTIMUM/CORRECTED MOISTURE CONTENT % 11.4 8.4 ALDOT SOIL-CEMENT 416-05AGE LOAD CYL DIA AREA STRENGTH DAYS POUNDS INCHES INCH² CORRECTION PSICONTROL AVERAGE OF 3 Samples 7 NR NR NR NR 620 WITH Wax EmulsionModifier of 7 12,150 3.99 12.51 0.91 880 the Invention AVERAGE OF 3Samples

Table 4 sets forth the mix designs utilized in compressing strengthevaluations, with the results set forth in Table 5.

TABLE 4 Compressive Strength Evaluation Test Mix Design PER 1 CUBIC YARDMIX DESIGN, POUNDS ASTM SLUMP/ POUNDS POUNDS STRENGTH EVALUATION CONTROLWITH ADDITIVE CEMENT 300 285 CLASS C FLY ASH 125 119 CONCRETE SAND 12631263 #57 GRAVEL NO 2195 2195 MOISTURE ADJUST WATER 148.5 132.5 WaxEmulsion Modifier 21.25 of the Invention

TABLE 5 ASTM C 1176 Compressive Strength ASTM C 1176 TEST CYLINDERS 6 ×12 INCHES ASTM WITH C 31 AVERAGE OF TWO SAMPLES CONTROL ADDITIVE  7 DAYAGE COMPRESSIVE STRENGTH, PSI 1970 2405 28 DAY AGE COMPRESSIVE STRENGTH,PSI 3035 3475

While the present invention has been described and illustrated byreference to particular embodiments and examples, those of ordinaryskill in the art will appreciate that the invention lends itself tovariations not necessarily illustrated herein. For this reason, then,reference should be made solely to the appended claims for purposes ofdetermining the true scope of the present invention.

1. A composition with an initial compressive strength of at least 2400psi comprising: (a) a paraffin hydrocarbon wax, (b) a saponifiable wax(c) a saponifier, (d) a dispersant, and (e) cement.
 2. The compositionof claim 1, wherein: (a) the paraffin hydrocarbon wax has a meltingpoint between about 50° C. to about 70° C., and (b) the saponifiable waxis a Montan wax having a melting point in the range of between about 70°C. to about 100° C., an acid number greater than 25, and asaponification number of greater than
 85. 3. The composition of claim 1,wherein the saponifier is ammonia hydroxide or an alkali metalhydroxide.
 4. The composition of claim 2, wherein the Montan wax ispresent in an amount of about 0.01 to about 20 parts, by weight, per 100parts of the paraffin hydrocarbon wax.
 5. The composition of claim 1,wherein the dispersant is polynaphthalenesulfonic acid present in anamount of about 0.1 to about 5 wt % based upon the weight of theemulsion.
 6. The composition of claim 1, comprising: (a) about 20 toabout 60 wt % of the paraffin hydrocarbon wax, based upon the weight ofthe emulsion; (b) about 0.01 to about 20 parts, by weight, of thesaponifiable wax, per 100 parts of the paraffin wax; (c) about 0.1 toabout 5 wt % of the saponifier, based upon the weight of the emulsion;(d) about 0.1 to about 5 wt % of the dispersant, based upon the weightof the emulsion; and (e) water.
 7. The composition of claim 1, whereinthe paraffin hydrocarbon wax, the saponifiable wax, the saponifier, andthe dispersant are provided in the form of an emulsion and is present inan amount of about 1 to about 25 gallons per cubic yard of the cement.8. The composition of claim 1, wherein the composition is a rollercompacted concrete.
 9. The composition of claim 1, wherein the cementcomprises a mixture of Portland cement and class 1 fly ash.
 10. Anemulsion for providing a cementitious composition with an initialcompressive strength of at least 2400 psi, consisting essentially of:(a) a paraffin hydrocarbon wax, (b) a saponifiable wax, (c) asaponifier, (d) a dispersant, and (e) water.
 11. The emulsion of claim10, wherein: (a) the paraffin hydrocarbon wax has a melting pointbetween about 50° C. to about 70° C., and (b) the saponifiable wax is aMontan wax having a melting point in the range of between about 70° C.to about 100° C., an acid number greater than 25, and a saponificationnumber of greater than
 85. 12. The emulsion of claim 10, wherein thesaponifier is ammonia hydroxide or an alkali metal hydroxide.
 13. Theemulsion of claim 10, wherein the Montan wax is present in an amount ofabout 0.01 to about 20 parts, by weight, per 100 parts of the paraffinhydrocarbon wax.
 14. The emulsion of claim 10, wherein the dispersant ispolynaphthalenesulfonic acid present in an amount of about 0.1 to about5 wt % based upon the weight of the emulsion.
 15. The emulsion of claim10, wherein the aqueous emulsion consists essentially of: (a) about38.68 wt % of Paraffin Wax, (b) about 1 wt % on Montan Wax, (c) about 1wt % of polynapthalenesulfonic acid dispersant, (d) about 0.25 wt % of45% aqueous potassium hydroxide, and (e) about 59.07 wt % water.
 16. Amethod for providing a cementitious composition, comprising: preparingan aqueous emulsion, for providing a cementitious composition with aninitial compressive strength of at least 2400 psi, the method comprisingcombining water, a paraffin hydrocarbon wax, a saponifiable wax and asaponifier, heating the combination to a temperature of between about185° F. (85° C.) to about 205° F. (96.1° C.); homogenizing the mixture;and blending the aqueous emulsion with at least cement.
 17. The methodof claim 16, wherein the paraffin wax is present in an amount of about20 to about 60 wt %, based upon the weight of the emulsion, and thesaponifiable wax is present in an amount of about 0.01 to about 20parts, by weight, per 100 parts of the paraffin wax.
 18. The method ofclaim 16, wherein: (a) the paraffin hydrocarbon wax has a melting pointbetween about 50° C. to about 70° C., and (b) the saponifiable waxcomprises a Montan wax having a melting point in the range of betweenabout 70° C. to about 100° C., an acid number greater than 25, and asaponification number of greater than
 85. 19. The method of claim 16,wherein the saponifier comprises ammonia hydroxide or an alkali metalhydroxide.
 20. The method of claim 16, wherein the dispersant comprisespolynaphthalenesulfonic acid in an amount of about 0.1 to about 5 wt %based upon the weight of the emulsion.